Failure Analysis of Mill Shaft Roll

A strip mill roll shaft failure was investigated. The investigation revealed that the fatigue strength of the shaft had been compromised by a combination of several factors that included: inadequate fillet radius size, the use of dissimilar filler materials to rebuild the shaft surface, the presence of slag inclusions at the weld/alloy interface, and machining defects on the shaft surface. Such failures have occurred repeatedly, and this paper presents a case study investigating the cause of the problem and discusses possible remedial measures to prevent similar occurrences.